North Korea has confirmed 15 more deaths and hundreds of thousands of additional patients with fevers as it mobilizes more than a million health and other workers to try to suppress the country’s first COVID-19 outbreak, state media reported Sunday.

After maintaining a widely disputed claim to be coronavirus-free for more than two years, North Korea announced Thursday that it had found its first COVID-19 patients since the pandemic began.

It has said a fever has spread across the country “explosively” since late April but hasn’t disclosed exactly how many COVID-19 cases it has found. Some experts say North Korea lacks the diagnostic kits needed to test a large number of suspected COVID-19 patients.

The additional deaths reported Sunday took the country’s reported fever-related fatalities to 42. The official Korean Central News Agency also reported that another 296,180 people with fevers had been tallied, taking the reported total to 820,620.

The outbreak has triggered concern about a humanitarian crisis in North Korea because most of the country’s 26 million people are believed to be unvaccinated against the coronavirus and its public health care system has been in shambles for decades. Some experts say North Korea might suffer huge fatalities if it doesn’t immediately receive outside shipments of vaccines, medicines and other medical supplies.

“Without COVID-19 test kits, North Korea is resorting to body temperature checks to guess at infections. But with such a very inferior and inaccurate method of examination, it’s impossible to find asymptomatic virus carriers and control viral surges,” said analyst Cheong Seong-Chang at South Korea’s Sejong Institute.

“As North Korea's (suspected) COVID-19 infections are explosively increasing, its death toll is expected to continue to rise," Cheong added.

Since Thursday, North Korea has imposed a nationwide lockdown to fight the virus. That could further strain the country’s fragile economy, which has suffered in recent years due to sharply reduced external trade caused by pandemic-related border shutdowns, punishing U.N. economic sanctions over its nuclear program and its own mismanagement, observers say.

During a meeting on the outbreak Saturday, North Korean leader Kim Jong Un described the outbreak as a historically “great upheaval” and called for unity between the government and people to stabilize the outbreak as quickly as possible.

KCNA said Sunday that more than 1.3 million people have been engaged in works to examine and treat sick people and raise public awareness of hygiene. It said everyone with fevers and others with abnormal symptoms was being put in quarantine and treated. KCNA said the elevated pandemic response includes the establishment of more quarantine facilities, the urgent transportation of medical supplies to hospitals and increased disinfection efforts.

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“All provinces, cities and counties of the country have been totally locked down and working units, production units and residential units closed from each other since the morning of May 12 and strict and intensive examination of all the people is being conducted,” KCNA said.

Of those with symptoms, 496,030 have recovered, while as of Saturday 324,4550 were still receiving treatment, KCNA reported, citing the country’s emergency epidemic prevention center.

State media reports said Kim and other senior North Korean officials are donating their private reserve medicines to support the country’s anti-pandemic fight. During Saturday’s meeting, Kim expressed optimism that the country could bring the outbreak under control, saying most transmissions are occurring within communities that are isolated from one another and not spreading from region to region.

Despite the outbreak, Kim has ordered officials to go ahead with planned economic, construction and other state projects, a suggestion that authorities aren’t requiring people to confine themselves at home. Hours after it admitted its virus outbreak Thursday, North Korea even fired ballistic missiles toward the sea in a continuation of its recent streak of weapons tests.

KCNA said that Kim, accompanied by top deputies, visited a mourning station Saturday set up for senior official Yang Hyong Sop, who died a day earlier, to express his condolences and meet bereaved relatives. A separate KCNA dispatch said Sunday that officials and laborers in the northeast were launching initiatives to prevent an expected spring drought from damaging crop yields and quality.

South Korea and China have offered to send vaccines, medical supplies and other aid shipments to North Korea, but Pyongyang hasn’t publicly responded to the overtures. North Korea previously rebuffed millions of doses of vaccines offered by the U.N.-backed COVAX distribution program amid speculation that it worried about possible side effects of vaccines or international monitoring requirements attached to those shots.

White House press secretary Jen Psaki said Thursday the United States supported international aid efforts but doesn’t plan to share its vaccine supplies with the North. The North Korean virus outbreak could still be a major topic of discussion when President Joe Biden visits Seoul later this week for a summit with newly inaugurated South Korean President Yoon Suk Yeol.

South Korea’s former spy chief Park Jie-won wrote on Facebook on Friday that he had proposed in May 2021 as the then-director of the National Intelligence Service that Washington send 60 million doses of vaccines to North Korea as humanitarian aid via COVAX. He said there were later talks in the U.N. and the Vatican about shipping 60 million doses to North Korea as well, but such aid was never realized as no formal offers were made to North Korea.

Park said he hopes North Korea would accept Yoon’s aid offers quickly though he said he doubts whether the North would do so.